1. Field of the Invention
This invention relates generally to a device for retaining a tarp on a movable vehicle, and more specifically to a device for retaining the free edge of a tarp fastened at an opposite edge to a vehicle having an open top for hauling.
2. Description of the Related Art
The industries that use open top transfer trailers often haul loads that are bulky, such as trash, mulch, and sawdust and will try to place as much product in the trailer as possible. Often the load is unevenly distributed, causing some areas of the trailer to become heaped up over the top of the trailer's sidewalls. These loads can blow out while traveling down the road. Therefore, these open-top trailers must have a cover installed over the trailer or truck bed whenever traveling on public roadways.
There are many methods and apparatuses used in the industry for covering an open top transfer trailer or truck bed. Tarps are widely used, but are very time consuming to install if they are free or “hand” tarps. In most operations where hand tarps are used, there is a scaffold or tarp rack at the loading station where the driver can pull the trailer and spread the tarp out over the load. If there is no tarp rack, the driver has to climb on top of the load and spread out the tarp, which is potentially dangerous due to a risk of falling. The driver then has to walk around the side of the trailer, hook straps to the tarp and pull the straps tight while hooking the straps to the trailer. These tarps are the least expensive method, but are by far the most time-consuming to install and the most dangerous for the driver.
A ratchet strap side roll tarp system is a second type of tarp used in this industry. This tarp has straps that are permanently attached to one side of the tarp and has a pipe attached along the same side of the tarp. The driver inserts a crank handle in the end of the pipe and rolls the tarp open and closed across the top of the trailer by cranking the handle. The straps hopefully fall over the edge of the trailer. The driver then threads each of the straps that are attached to the tarp through ratchets attached to the bottom of the trailer and then tightens the tarp. This system allows the driver to open and close the tarp from the ground rather than up high at the top of the trailer. However, the straps may become trapped between the tarp and the load, forcing the driver to use a long pole to retrieve the straps or climb on top of the load and free the straps manually. Additionally, on a windy day a strap may flap about making it difficult for the driver to capture the strap for securing it to the truck. This system also consumes a lot of time in requiring the driver to thread each strap through each ratchet every time the trailer is filled and emptied.
The Shur-Co. (Yankton, S. Dak.) Shurlock Side Roll Tarp System has a tarp that is similar to the ratchet system described above, but there are no straps on the tarp. The Shurlock system has a single latch plate that is permanently attached to the topside rail of the trailer at one side edge and extends the entire length of the trailer. To operate this system, the driver cranks the crank handle to roll the tarp across the trailer, the tarp roll pipe is then tightened under the latch plate and the crank handle is locked to the side or back of the trailer.
One significant problem with this system is that it does not account for “heaping” of the load that is common. Because the entire length of the free tarp edge is tightened to the same extent, the tarp does not tighten properly when the load has heights that vary along the trailer length. Instead, the tarp is very tight around the heaped portion of the load, but loose in areas that are not piled as high in the trailer. This may cause the tarp to flap and tear in the wind.
The Donavan Enterprises, Inc. (Stuart, Fla.) SideWinder system is also made for the open top transfer trailer. The SideWinder has a steel frame that fits on top of the trailer and has a mesh tarp attached to the frame. The frame is hooked to a hydraulic ram and an electric pump that opens and closes the tarp. The frame and tarp are moved as a unit up and over the load and connected on the opposite side of the trailer to a cable. The problem with this system is that it is very expensive and may require very frequent maintenance.
Therefore, there is a need for a tarp system that overcomes the deficiencies of the prior art.